The present invention relates to the field of memory-programmable controllers for controlling peripheral processes and having cyclically traversed user control programs. In particular, the present invention relates to memory-programmatic controllers of the multi-processor type including a word processor for processing operating system and word commands, a bit processor for processing binary interlinking commands, an operating system memory in which an operating system program is stored, a user program memory in which the control program is stored, a data memory having binary process images stored therein, peripheral modules coupled to the process being controlled and buses for coupling the above-mentioned components.
Memory-programmable controllers are described in detail, for instance, in the journal Siemens Energietechnik 1979, no. 2, pages 43 to 47, no. 4, pages 136 to 139, in the journal Siemens Energietechnik 1980, no. 9, pages 360 to 363 and also in European Patent No. 10170 and U.S. Pat. Nos. 3,921,146 and 3,942,158.
A memory-programmable controller should preferably be able to perform logical linkages of data one bit wide as well as complex functions with word-wide data, for instance, arithmetic functions, data transfer, timing and counting processes. It is essential in this connection that purely binary linking commands are traversed very much more frequently than the more complex word oriented functions. The operating time of the overall program and therefore, the reaction time of the controller, depends considerably more on the execution time of the binary linking commands than on the processing time required for the more complex functions.
It is therefore advantageous to use, as the controller, a multiprocessor system, in which the execution of the binary commands is assigned to a separate fast bit processor, while a relatively slow word processor carries out the complex functions (see, for instance, the journal Siemens Energietechnik 1980, no. 9, page 361). In this known memory-programmable controller with a word and a bit processor, the input and output modules are also connected to the buses of the controller. Since these buses must therefore leave the process or modules and must possibly also go beyond the housing frame of the controller proper, relatively long bus running times and thereby, relatively long command execution times result.